Microlenses for an image sensor such as a charge coupled device (CCD) or LCDs (liquid crystal panels) have been designed to have increased light collection or light extraction efficiency by combining a high refractive index material and a low refractive index material.
For example, the following design is generally adopted. A high refractive index material is used for a planarization film in a charge coupled device (CCD) and a low refractive index material is used for a microlens so as to collect light while preventing reflection. Alternatively, a high refractive index material is used for a microlens so as to collect light even when the lens is far from a diode.
Meanwhile, in recent years, LCDs are shifting toward a larger screen, higher definition, and lower power consumption, which requires the light extraction efficiency of LCDs to be enhanced. A common method to achieve it is to use coating of a low refractive index material to enhance the light extraction efficiency.
In this method, a resist composition containing a polymer resin with a high refractive index and a crosslinkable material with a high refractive index is used to coat a substrate for film formation, and the resultant workpiece is subjected to patterning and development by a photolithography technique to form a pattern, and to obtain a planarization film or a spacer for an LCD. Etching and similar processes are further performed to form a microlens.
It is described that a photosensitive composition that includes a resin obtained by condensing a bisphenol fluorene-type epoxy acrylate and a tetracarboxylic dianhydride is used for a protective layer and an interlayer insulating film in a color filter, a liquid crystal display device, an integrated circuit device, a solid-state image sensor, and the like (Patent Document 1, Patent Document 2, and Patent Document 3).